The porthole areas of such heat exchanger plates of a plate heat exchanger are subjected to strong and varying loads during operation of the plate heat exchanger. When the pressure increases in every second plate interspace, large pulling forces arise in the porthole areas, which tend to pull adjacent heat exchanger plates apart, especially in case of brazed or welded plate heat exchangers. In particular, large forces will thus appear at and around the contact zones of the beams in the porthole areas.
Providing the contact zones at the end portions of the beams is disadvantageous since the thickness of the material of the porthole areas of the heat exchanger plate is thinnest at the end portion of the beam, where the material is bent and deformed in several directions. Therefore the end portions are not suitable for taking up large loads. If the contact zones are located at the end portions of the beams there will thus exist a risk for cracks in the material of the heat exchanger plates.
Plate heat exchangers, where the beams of the heat exchanger area continues in the same direction into the porthole area, will have irregularly positioned contact zones in the porthole area. In other words some contact zones will be located close to the porthole and some more remote from the porthole. Furthermore, the distance between adjacent contact zones in the porthole area will vary around the porthole. This is disadvantageous with regard to the strength of the porthole area.
U.S. Pat. No. 8,109,326 discloses a heat transfer plate intended to constitute, together with other heat transfer plates, a plate stack with permanently connected plates for a heat exchanger, which heat transfer plate has a first long side and an opposite second long side, a first short side and an opposite second short side, a heat transfer surface exhibiting a pattern of ridges and valleys, first and second port regions, the first port region being situated in a first corner portion formed at the meeting between the first long side and the first short side, the second port region being situated in a second corner portion formed at the meeting between the second long side and the first short side, and the first port region being connected to a number of ridges and valleys, which ridges and valleys have in principle an extent from the first port region diagonally towards the second long side.
WO 201173083 discloses a heat exchanger plate including a bottom that has four fluid passage openings placed, respectively, in four corner regions, said bottom being provided with chevron-patterned waves extending from both sides of a median longitudinal axis of the plate. The waves of the plate are intended to intersect with the waves of an identical adjacent plate in a vertically adjacent relationship in which both plates are rotated 180°, thus forming point-by-point contact areas for the mutual brazing thereof. The bottom has, in the corner regions and near the passage openings, supplementary raised areas that are capable of defining supplementary point-by-point contact areas for the brazing, thus making it possible to improve the resistance to pressure from the heat exchanger.